Polyethylene for preparing fiber and preparation method of the same

Abstract

The present disclosure relates to a polyethylene suitable for preparing fibers with enhanced yellow index and filterability in the spinning process by having improved aging lifetime of the polyethylene, and a preparation method of the same.

1 . A polyethylene satisfying the following:
 a melt index measured at a temperature, 190° C., under a load of 2.16 kg according to ASTM D 1238 is 15 g/10 min to 40 g/10 min,   a melt flow rate ratio (MFRR) is 3 or less, wherein the melt flow rate ratio (MFRR) is calculated by dividing a melt index measured at 190° C. under a load of 5 kg (MI 5 ) by a melt index measured at 190° C. under a load of 21.6 kg (MI 21.6 ),   a content of alkaline earth metals and transition metals measured by inductively coupled plasma (ICP) spectroscopy is 0.8 ppm or less, and   a halogen content measured by combustion ion chromatography (IC) is 5 ppm or less.   
     
     
         2 . The polyethylene of  claim 1 , wherein the melt index is 18 g/10 min to 33 g/10 min. 
     
     
         3 . The polyethylene of  claim 1 , wherein the melt flow rate ratio (MFRR) is 2 to 3. 
     
     
         4 . The polyethylene of  claim 1 , wherein a molecular weight distribution (Mw/Mn) is 2.0 to 2.6. 
     
     
         5 . The polyethylene of  claim 1 , wherein a density measured at a temperature 23° C. according to ASTM D 1505 is 0.945 g/cm 3  to 0.965 g/cm 3 . 
     
     
         6 . The polyethylene of  claim 1 , wherein the polyethylene is a copolymer of ethylene, and at least one comonomer selected from the group consisting of propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. 
     
     
         7 . A method for preparing the polyethylene according to  claim 1 , comprising polymerizing one or more olefinic monomers in presence of a hybrid supported metallocene catalyst,
 wherein the hybrid supported metallocene catalyst comprises a first cocatalyst, at least one first metallocene compound represented by Chemical Formula 1, at least one second metallocene compound represented by Chemical Formula 2, and a second cocatalyst, all of which are supported on a support, and   wherein the hybrid supported metallocene catalyst is prepared by:   supporting the first metallocene compound of Chemical Formula 1 on the support;   supporting the first cocatalyst on the support;   supporting the second metallocene compound of Chemical Formula 2 on the support; and   supporting the second cocatalyst on the support:
   (Cp 1 R a ) n (Cp 2 R b )M 1 Z 1   3-n   [Chemical Formula 1]
 
   wherein in Chemical Formula 1,   M 1  is a Group 4 transition metal;   Cp 1  and Cp 2  are the same as or different from each other, and each independently is any one selected from the group consisting of cyclopentadienyl, indenyl, 4,5,6,7-tetrahydro-1-indenyl, and fluorenyl radical, wherein Cp 1  and Cp 2  are optionally substituted with C 1-20  hydrocarbon;   R a  and R b  are the same as or different from each other, and each independently is hydrogen, substituted or unsubstituted C 1-20  alkyl, substituted or unsubstituted C 1-10  alkoxy, substituted or unsubstituted C 2-20  alkoxyalkyl, substituted or unsubstituted C 6-20  aryl, substituted or unsubstituted C 6-10  aryloxy, substituted or unsubstituted C 2-20  alkenyl, substituted or unsubstituted C 7-40  alkylaryl, substituted or unsubstituted C 7-40  arylalkyl, substituted or unsubstituted C 8-40  arylalkenyl, or substituted or unsubstituted C 2-10  alkynyl;   Z 1  are each independently a halogen atom, substituted or unsubstituted C 1-20  alkyl, substituted or unsubstituted C 2-10  alkenyl, substituted or unsubstituted C 7-40  alkylaryl, substituted or unsubstituted C 7-40  arylalkyl, substituted or unsubstituted C 6-20  aryl, substituted or unsubstituted C 1-20  alkylidene, substituted or unsubstituted amino, substituted or unsubstituted C 2-20  alkylalkoxy, or substituted or unsubstituted C 7-40  arylalkoxy; and   n is 1 or 0;   
       
         
           
           
               
               
           
         
         wherein in Chemical Formula 2, 
         B is boron, 
         M is a group 4 transition metal, 
         R 1  to R 4  are each independently hydrogen, substituted or unsubstituted C 1-20  alkyl, substituted or unsubstituted C 3-20  cycloalkyl, or substituted or unsubstituted C 6-20  aryl, or R 1  and R 2  or R 3  and R 4  are bonded to each other to form a substituted or unsubstituted C 6-60  aromatic ring, 
         R 5  and R 6  are each independently substituted or unsubstituted C 1-20  alkyl, substituted or unsubstituted C 3-20  cycloalkyl, or substituted or unsubstituted C 6-20  aryl, or R 5  and R 6  are bonded to each other to form a substituted or unsubstituted C 3-60  aliphatic ring or a substituted or unsubstituted C 6-60  aromatic ring, 
         X 1  and X 2  are each independently substituted or unsubstituted C 1-20  alkyl or —O(CO)R′, wherein R′ is C 1-20  alkyl, 
         Q is a substituted or unsubstituted C 2-60  heterocyclic ring containing at least one selected from the group consisting of N, O and S, 
         Y and Y′ are elements constituting Q, 
         Y is N, O, or S, and 
         Y′ is an element of Q and adjacent to Y, and Y′ is N or C. 
       
     
     
         8 . The method for preparing the polyethylene of  claim 7 , wherein the first metallocene compound and the second metallocene compound are supported on the support in a molar ratio of 3:1 to 1:10. 
     
     
         9 . The method for preparing the polyethylene of  claim 7 , wherein the second cocatalyst comprises a borate-based cocatalyst, and a molar ratio of a total metal contained in the hybrid supported metallocene catalyst to boron contained in the second cocatalyst is 1:0.45 to 1:3. 
     
     
         10 . The method for preparing the polyethylene of  claim 7 , wherein the first cocatalyst comprises at least one selected from compounds represented by Chemical Formulae 3 and 4:
   —[Al(R 31 )—O] m —  [Chemical Formula 3]
   wherein in Chemical Formula 3,   R 31  are the same as or different from each other, and each independently halogen; or C 1-20  hydrocarbyl substituted or unsubstituted with halogen; and   m is an integer of 2 or more,
   D(R 41 ) 3   [Chemical Formula 4]
 
   wherein in Chemical Formula 4,   D is aluminum or boron, and   R 41  are the same as or different from each other, and each independently halogen; or C 1-20  hydrocarbyl substituted or unsubstituted with halogen.   
     
     
         11 . The method for preparing the polyethylene of  claim 7 , wherein the second cocatalyst comprises a borate compound represented by Chemical Formula 5 or Chemical Formula 6:
   [L-H] + [ZA 4 ] −   [Chemical Formula 5]
     [L] + [ZA 4 ] −   [Chemical Formula 6]
   wherein in Chemical Formulae 5 and 6,   L are each independently a neutral or cationic Lewis base;   H is a hydrogen atom;   Z are each independently boron; and   A are the same as or different from each other, and each independently C 6-20  aryl or C 1-20  alkyl, wherein the C 6-20  aryl or C 1-20  alkyl is unsubstituted or substituted with at least one substituent selected from the group consisting of halogen, C 1-20  alkyl, C 1-20  alkoxy and C 6-20  aryloxy.   
     
     
         12 . The method for preparing the polyethylene of  claim 7 , wherein the second cocatalyst includes trimethylammonium tetrakis(pentafluorophenyl)borate, triethylammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium n-butyltris(pentafluorophenyl)borate, N,N-dimethylanilinium benzyltris(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(4-(t-butyldimethylsilyl)-2,3,5,6-tetrafluorophenyl)borate, N,N-dimethylanilinium tetrakis(4-(triisopropylsilyl)-2,3,5,6-tetrafluorophenyl)borate, N,N-dimethylanilinium pentafluorophenoxytris(pentafluorophenyl)borate, N,N-dimethyl-2,4,6-trimethylanilinium tetrakis(pentafluorophenyl)borate, trimethylammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate, N,N-dimethylanilinium tetrakis(2,3,4,6-tetrafluorophenyl)borate, hexadecyldimethylammonium tetrakis(pentafluorophenyl)borate, N-methyl-N-dodecylanilinium tetrakis(pentafluorophenyl)borate, or methyldi(dodecyl)ammonium tetrakis(pentafluorophenyl)borate.